A number of computer screen cursor or pointing control devices have been developed in recent years which allow the user of a device, in particular computers, to selectively position the cursor or pointing device in use at any X,Y coordinate pair on a computer screen or plotting device or any such graphical display.
Typical of the devices previously available is the trackball-type mechanism shown in U.S. Pat. No. 4,404,865 to Kim, U.S. Pat. No. 4,933,670, to Wislocki and U.S. Pat. No. 4,952,919 to Nippoldt. The central feature of these type devices is the use of an individual sphere which is supported on bearings permitting rotation of the sphere in any direction about a central axis. Motion detection devices are biased against the sphere which permit detection of sphere movement. The detected sphere movement is converted into X-axis and Y-axis components which are then utilized to reposition a pointing device or a cursor.
It has also been typical of this art to invert the trackball mechanism permitting the sphere to be suspended from the bottom of a housing. The sphere or trackball is then rotated by movement of the housing about a suitable surface capable of providing frictional contact with the trackball. Movement of the housing then generates movement of the trackball which is then communicated to the pointing device or the computer screen. This form of trackball control device is typically referred to as a mouse.
The trackball-type device and the mouse-type device present a number of problems to computer users and in particular users of portable or laptop computers. The mouse-type control device presents the drawback of requiring a surface of adequate size to permit movement of the mouse about an area sufficient to direct the cursor into all areas of the computer screen. If the space available is of insufficient size it is necessary to lift the mouse from the surface and reposition it in order to continue to move the mouse in the selected direction to achieve complete movement of the cursor or pointer across the entirety of the computer screen or plotter device. The unavailability of such sufficient surface area during travel has prompted increased use of the trackball-type device with portable computers.
Typically the trackball device is attached to the edge of the portable computer keyboard or embedded in some central location of the portable computer keyboard or included in a wand-type device which may be held by the user in order to rotate the trackball. While the trackball-type devices do not require the surface space necessary for movement of the mouse-type device, the trackball-type devices do present a small active control surface area for contact with the thumb or other digit of a user in order to achieve rotation of the trackball. The small surface area of the trackball often requires an increase in the ratio between the actual movement of the trackball and the movement of the cursor on the screen in order to move the cursor from top-to-bottom or left-to-right on the screen without an inordinate number of rotations of the trackball.
This can lead to very rapid and jumpy movement of the cursor or pointer and the inability to achieve fine control of the cursor position on the computer screen. An additional problem found with mouse-type devices and with side-mounted trackball devices is that the hand of the computer user must be taken from the keyboard in order to actuate the mouse or trackball. This tends to slow operation of the computer and can represent a substantial inconvenience to the user when repositioning of the cursor or pointer is frequently necessary.
Recently attempts have been made to avoid the drawbacks of the conventional mouse and trackball-type devices by incorporating elongated bar-type devices at the base of the keyboard in order to permit a user to maintain keyboard hand position while utilizing the thumb to manipulate a cursor positioning bar. Examples of such bar-type repositioning devices may be found U.S. Pat. No. 4,982,618 to Culver and U.S. Pat. No. 5,270,690 to Oberg.
In the patent to Culver the bar control mechanism provides a continuous rotational type of movement as the bar is moved about its longitudinal axis. However, when the device of Culver is operated in the plane of its longitudinal axis it will come to a positive stop as the end of the rod contacts a structural obstacle such as the keyboard housing or the detector for movement in the plane of the longitudinal axis. This physical limitation of movement in the longitudinal axis of the device of Culver presents the requirement that the device be brought into registration with the computer screen size or plotter bed size so that when the lateral movement to either the left or right comes to a physical stop the cursor will have reached the full left or full right position on the computer screen. It will be appreciated that such a limitation on the movement of the control device will result in a limitation on the ratio of control device movement to cursor movement and that a 1:1 ratio between these parameters cannot be achieved and still maintain the rod structure within the confines of the keyboard housing or structure of the laptop computer.
The device of Oberg provides multiple longitudinally extending belts. However, each of these belts operates independently from one another and movement of one belt does not provide movement of the adjacent belts. Therefore, an operator of the device must select the particular belt which is in contact with the rotating wheel of Oberg, or more generally, the movement sensor, in order to effect movement of the cursor. Alternatively, if the operator selects the band of Oberg which is most convenient to the operator's thumb this band may not be in contact with the pickup wheel or rotating wheel of Oberg and movement of the band will communicate no information and achieve no response in the cursor or pointer.
Therefore, it may be seen that the need is present for a cursor or pointer control device which can take advantage of the limited space available in a computer keyboard or laptop computer case to provide a user with a large surface contact area proximate to the hand while in the typing position and which offers an uninterrupted or continuous path of travel to permit selection any ratio of control device movement to cursor movement and to avoid any need to align the movement limits of the control device with the screen dimensions of a computer screen or other display device.